His remarks came after Iran rejected Western calls to "stand down" its threat of reprisals.

Iran has vowed to avenge the death of Haniyeh in Tehran on July 31, which came hours after an Israeli strike in Beirut killed a senior commander of Hezbollah.

Asked if a truce between Israel and Hamas could stave off an Iranian assault, Biden said: "That's my expectation".

He told reporters in New Orleans that while negotiations were "getting hard" he was "not giving up".

Western diplomats have scrambled to prevent a major conflagration in the Middle East, where tensions were already high due to the Israeli war on Gaza.

"Ten months since the start of the war, the threat of further regional escalation is more palpable, and chilling, than ever," said Rosemary DiCarlo, United Nations undersecretary-general for political and peacebuilding affairs.

She called on all parties to "end all escalatory rhetoric and actions".

In a statement on Monday, the United States and its European allies urged Iran to de-escalate.

The White House warned that a "significant set of attacks" by Iran and its allies was possible this week, saying Israel shared the same assessment.

The United States has deployed an aircraft carrier strike group and a guided missile submarine to the region in support of Israel.

Iran's foreign ministry spokesman Nasser Kanani criticised the Western call for restraint.

"The declaration by France, Germany and Britain, which raised no objection to the international crimes of the Zionist regime, brazenly asks Iran to take no deterrent action against a regime which has violated its sovereignty and territorial integrity," he said in a statement.

Far-right minister opposes talks 

The United States and its European allies also called for a ceasefire between in Gaza, with truce talks to resume on Thursday.

Far-right parties in Prime Minister Benjamin Netanyahu's ruling coalition strongly oppose any ceasefire in Gaza, a point rammed home by firebrand National Security Minister Itamar Ben Gvir on a visit to Jerusalem's flashpoint Al-Aqsa Mosque compound.

The visit was swiftly condemned by Al-Aqsa's custodian Jordan, as well as world powers including the United States, the European Union and the United Nations.

Defying longstanding rules that allow Jews and other non-Muslims to visit the compound but not to pray there, Ben Gvir led thousands of Israelis in singing Jewish hymns and performing Talmudic rituals.

In a video filmed inside the compound, Ben Gvir renewed his opposition to any let-up in the Gaza war.

"We must win and not go to the talks in Doha or Cairo," the minister said, referring to the truce talks planned for Thursday.

US State Department spokesman Vedant Patel nonetheless said Washington remained hopeful that talks would move forward.

Netanyahu has already confirmed Israel's participation and "our Qatari partners have assured us that they are working to ensure that there is Hamas representation as well," Patel told reporters.

Hamas has urged mediators to implement a truce plan presented earlier by Biden instead of holding more talks.